The present invention relates to the preparation of detergent acid mix compositions containing benzoic acid. The benzoic acid substantially reduces the viscosity of the acid mix formed in the reaction of an ethoxylated alcohol, alkyl benzene, fatty alcohol, or other sulfatable detergent precursor with the sulfating agent. The use of the term "sulfating agent" throughout the specification and claims includes, but is not limited to, oleum, 100% sulfuric acid, chlorosulfonic acid, and sulfur trioxide. The use throughout this application of the term "viscosity aid" is defined to mean a material which will reduce the viscosity of a detergent acid mix comprising the organic sulfuric or sulfonic acid as well as sulfating agent or unreacted detergent precursor present. For the purposes of this application, the term "sulfation", unless otherwise indicated, may be used interchangeably with "sulfonation".
The strength of the sulfating agent may be expressed in many forms. The apparent acid strength is expressed as the percentage of sulfuric acid which would be formed if sufficient water were present to convert all the sulfur trioxide to sulfuric acid. The term "acid strength" relates to the concentration of sulfur trioxide in oleum. If the sulfating agent is sulfuric acid, the acid concentration must be 100% as sulfuric acid is not a particularly effective sulfating agent. Spent acid strength is a measure of the final concentration of the sulfating agent remaining after the sulfation reaction. A critical spent acid strength exists for most detergent precursors below which the sulfation reaction will not proceed effectively. The percentage of spent acid strength is given by the following formula: ##EQU1## where (excess SO.sub.3) is the sulfur trioxide introduced to the reaction over and above that used in the sulfation. The excess sulfur trioxide is subsequently neutralized to form sodium sulfate. The quantity (H.sub.2 O) is the water introduced into the system during the sulfation process. The percentage spent acid strength is a measure of the available sulfur trioxide which may be used for sulfation. In other words, where the sulfur trioxide would react on a one-to-one mole basis with the detergent precursor to give a sulfated product, the addition of water to the system will lower the amount of sulfur trioxide available for sulfation of the detergent precursor.
Toluene, xylene, cumene, and benzene are sulfatable materials known in the art as having utility in their sulfonated form in reducing acid mix viscosity. Toluene is the most widely used material for reducing the viscosity of detergent acid mix compositions and is exemplary of the other sulfatable viscosity aids. The use of toluene as well as the other sulfatable viscosity aids is not without substantial drawbacks. One such drawback in the use of toluene as a viscosity aid arises because toluene is very reactive in the presence of sulfating agents. Thus, when toluene is sulfonated in the presence of a less reactive organic compound, the toluene is preferentially sulfonated to toluene sulfonic acid.
Toluene as a viscosity aid at high acid strengths is undesirable in that the toluene sulfonic acid may continue to react with the sulfating agent to form disulfonic acids in the ortha and meta positions, thus using more sulfating agent than is required with unpredictable results. If toluene is sulfonated in the presence of a more reactive organic compound, the completeness of toluene sulfonation will be lessened with potential side reactions of the detergent precursor occurring. Incomplete sulfonation of an aromatic sulfonatable viscosity aid will result in the aromatic compound being processed through the crutcher with evaporation from the crutcher mix, or, if the product is spray-dried, a "plume" may be emitted from the drying towers.
Thus the sulfonation of toluene requires in many cases that the toluene be sulfonated in the absence of the detergent precursor, therefore requiring additional equipment if the process is to be continuous.
The preparation of detergent compositions ordinarily requires that the acid mix be neutralized. As toluene may form a mono- or di-sulfonic acid when sulfonated, it is apparent that at least one mole of caustic will be required to neutralize each mole of sulfonate to be formed. The previously mentioned neutralization steps are costly in the use of excessive amounts of base. The exothermic sulfonation of toluene and subsequent neutralization of toluene sulfonic acid impose an additional heat exchange load on the system. Thus the use of a non-sulfatable viscosity aid will reduce heat transfer requirements while using less caustic. As some sulfuric acid is usually present in all sulfation reactions, sodium sulfate will be present in the final product from neutralization. By using a non-sulfatable viscosity aid, the amount of sulfating agent used is reduced and thus less sodium sulfate is formed leaving more room in the formula. The foregoing advantages are equally applicable to the replacement of benzene, cumene, and xylene by a non-sulfatable viscosity aid.
Aromatic sulfonate salts such as toluene sulfonate have been used as anti-caking agents in spray-dried phosphate-containing granular detergent compositions. However, when phosphate builders are eliminated from spray-dried detergent compositions, the presence of aromatic sulfonates may aggravate the caking tendencies of the detergent product. The viscosity aid of the present invention is also a novel anti-caking aid for use with non-phosphate built granular detergent products. Benzoate salts as anti-caking aids are discussed in the commonly assigned and concurrently filed U.S. Pat. application of J. A. Sagel and C. E. Weber having Ser. No. 523,391 and a filing date of Nov. 13, 1974 now U.S. Pat. No. 3,932,316 and further discussed in the commonly assigned and concurrently filed U.S. Pat. application of J. A. Sagel and C. E. Weber having Ser. No. 523,392 and a filing date of Nov. 13, 1974, both incorporated herein by reference.
Accordingly, it is an object of the present invention to provide a process for reducing the viscosity of a detergent acid mix composition.
It is a further object of the present invention to eliminate or substantially reduce the amount of toluene sulfonate used in the processing of non-phosphate granular detergents.
It is a further object of the present invention to provide a viscosity aid which does not sulfonate in the process of preparing an organic sulfuric or sulfonic acid mix composition.
It is a particular object of the present invention to provide a process in which a non-sulfatable viscosity aid substantially lowers the viscosity of an alkyl ether sulfuric acid in an acid mix.
It has been discovered that during the sulfation of detergent precursors such as an alkyl benzene, fatty alcohol, or an ethoxylated alcohol, with oleum, sulfuric acid, chlorosulfonic acid, or sulfur trioxide that the viscosity of the resultant composition can be substantially reduced by carrying out the sulfation process in the presence of benzoic acid. The benzoic acid when used in the instant sulfation process remains essentially unreacted.
Percentages and ratios given throughout the application are by weight unless otherwise indicated. The use of the term "alkyl" means branched as well as straight-chained material. Temperatures are in Fahrenheit unless indicated otherwise.